Mechanical Behavior of in-situ Chondrocyte at Different Loading Rates: A Finite Element Study

Previous findings indicated that in-situ chondrocytes die readily following impact loading, but remain essentially unaffected when loaded at the same magnitude but with a slow (non-impact) loading rate. The current study was aimed at identifying the causes for cell death in impact loading by quantifying chondrocyte mechanics when cartilage was compressed nominally by 5% at different loading rates.. Multiscale modeling techniques were used. Cartilage was modeled accounting for collagen stiffening in tension. Chondrocytes were modelled to be including the cell membrane, pericellular matrix, and pericellular capsule. The results showed that cell deformations were lowest and cell fluid pressures were highest for the highest (impact) loading rate. Tangential strain rates on the cell membrane were highest at the highest loading rate and occurred primarily in superficial tissue cells. Since cell death following impact loading was primarily observed in superficial zone cells, we speculate that cell death in impact loading is caused by the high membrane strain rates observed in these cells for simulated impact loading conditions. Keywords— Finite Element Modeling; impact; chondrocyte; cell mechanics; cell death.